Originally Posted by
bluewar02
Hi I have an 03 f-150 xlt 4.2 I changed the motor about a year ago it has about 50k on it the issue i am having is it's revving up and down when it's cold when it fully warms up it runs great I changed the fuel filter, spark plugs and wires I changed the IAC motor, cleaned the MAF sensor, I unplugged the throttle position sensor power plug then started the truck to see if it was bad but the same thing happen, I started the truck again and unplugged the IAC was bad again but the idle just got a little lower the truck did not shut off so I guess that's good I checked for air leaks and that seems to be good no vac leaks I'm not sure what else to do any advice would be great thanks